The present invention relates to methods and apparatus for exposure illumination for use in projection exposure apparatus for producing semiconductor chips, and more particularly, to projection exposure apparatus, illumination methods and illumination apparatus which control the directivity of illuminating light in accordance with the size and shape of a pattern to be exposed or detected as well as the kind of a mask, a reticle or a wafer, so as to allow a pattern to be exposed or detected in an appropriate condition.
Patterns of semiconductor integrated circuits tending to be increasingly fine have advanced to an extent that the pattern width approaches to the wavelength of light. Although exposing methods using X-rays or electron rays in place of light beams have been developed, these methods are inferior in mass productivity as compared with the light exposing method which allows a large number of integrated circuit chips to be exposed for a short time, particularly for producing memories and so on which are in great demand, and therefore encounter difficulties in mass-producing inexpensive memories. In such circumstances, techniques have been developed in recent years for providing a mask or a reticle used in a conventional i-line reduction projection exposure apparatus (i-line stepper) with a phase shift portion so as to significantly improve the resolution of a pattern as compared with a conventionally used normal reticle. Further, a technique, as described in JP-A-61-91662, has been developed for improving the resolution of patterns, even without employing such a special reticle, by forming an ring-shaped light beam for illuminating a reticle on an entrance pupil of a reduction projection lens so as to have high spatial frequency spectrum of the light transmitting the reticle pass through an entrance pupil of an imaging lens for exposure.
When a method of improving the resolution of patterns as described above is to be employed, if a conventionally used semiconductor exposure apparatus (i-line stepper) is used as it is, a problem arises that a so-called .sigma. value indicative of the illumination directivity of a light beam illuminating a reticle (.sigma.=the ratio of extension of illuminating light on a pupil of an imaging lens for exposure to the diameter of the pupil of the lens) does not coincide with the .sigma. value indicative of the illumination directivity optimal to the resolution improving method.